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TOMOYO Linux Cross Reference
Linux/include/linux/uaccess.h

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  1 #ifndef __LINUX_UACCESS_H__
  2 #define __LINUX_UACCESS_H__
  3 
  4 #include <linux/sched.h>
  5 #include <linux/thread_info.h>
  6 #include <linux/kasan-checks.h>
  7 
  8 #define VERIFY_READ 0
  9 #define VERIFY_WRITE 1
 10 
 11 #define uaccess_kernel() segment_eq(get_fs(), KERNEL_DS)
 12 
 13 #include <asm/uaccess.h>
 14 
 15 /*
 16  * Architectures should provide two primitives (raw_copy_{to,from}_user())
 17  * and get rid of their private instances of copy_{to,from}_user() and
 18  * __copy_{to,from}_user{,_inatomic}().
 19  *
 20  * raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
 21  * return the amount left to copy.  They should assume that access_ok() has
 22  * already been checked (and succeeded); they should *not* zero-pad anything.
 23  * No KASAN or object size checks either - those belong here.
 24  *
 25  * Both of these functions should attempt to copy size bytes starting at from
 26  * into the area starting at to.  They must not fetch or store anything
 27  * outside of those areas.  Return value must be between 0 (everything
 28  * copied successfully) and size (nothing copied).
 29  *
 30  * If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
 31  * at to must become equal to the bytes fetched from the corresponding area
 32  * starting at from.  All data past to + size - N must be left unmodified.
 33  *
 34  * If copying succeeds, the return value must be 0.  If some data cannot be
 35  * fetched, it is permitted to copy less than had been fetched; the only
 36  * hard requirement is that not storing anything at all (i.e. returning size)
 37  * should happen only when nothing could be copied.  In other words, you don't
 38  * have to squeeze as much as possible - it is allowed, but not necessary.
 39  *
 40  * For raw_copy_from_user() to always points to kernel memory and no faults
 41  * on store should happen.  Interpretation of from is affected by set_fs().
 42  * For raw_copy_to_user() it's the other way round.
 43  *
 44  * Both can be inlined - it's up to architectures whether it wants to bother
 45  * with that.  They should not be used directly; they are used to implement
 46  * the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
 47  * that are used instead.  Out of those, __... ones are inlined.  Plain
 48  * copy_{to,from}_user() might or might not be inlined.  If you want them
 49  * inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
 50  *
 51  * NOTE: only copy_from_user() zero-pads the destination in case of short copy.
 52  * Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
 53  * at all; their callers absolutely must check the return value.
 54  *
 55  * Biarch ones should also provide raw_copy_in_user() - similar to the above,
 56  * but both source and destination are __user pointers (affected by set_fs()
 57  * as usual) and both source and destination can trigger faults.
 58  */
 59 
 60 static __always_inline unsigned long
 61 __copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
 62 {
 63         kasan_check_write(to, n);
 64         check_object_size(to, n, false);
 65         return raw_copy_from_user(to, from, n);
 66 }
 67 
 68 static __always_inline unsigned long
 69 __copy_from_user(void *to, const void __user *from, unsigned long n)
 70 {
 71         might_fault();
 72         kasan_check_write(to, n);
 73         check_object_size(to, n, false);
 74         return raw_copy_from_user(to, from, n);
 75 }
 76 
 77 /**
 78  * __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
 79  * @to:   Destination address, in user space.
 80  * @from: Source address, in kernel space.
 81  * @n:    Number of bytes to copy.
 82  *
 83  * Context: User context only.
 84  *
 85  * Copy data from kernel space to user space.  Caller must check
 86  * the specified block with access_ok() before calling this function.
 87  * The caller should also make sure he pins the user space address
 88  * so that we don't result in page fault and sleep.
 89  */
 90 static __always_inline unsigned long
 91 __copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
 92 {
 93         kasan_check_read(from, n);
 94         check_object_size(from, n, true);
 95         return raw_copy_to_user(to, from, n);
 96 }
 97 
 98 static __always_inline unsigned long
 99 __copy_to_user(void __user *to, const void *from, unsigned long n)
100 {
101         might_fault();
102         kasan_check_read(from, n);
103         check_object_size(from, n, true);
104         return raw_copy_to_user(to, from, n);
105 }
106 
107 #ifdef INLINE_COPY_FROM_USER
108 static inline unsigned long
109 _copy_from_user(void *to, const void __user *from, unsigned long n)
110 {
111         unsigned long res = n;
112         might_fault();
113         if (likely(access_ok(VERIFY_READ, from, n))) {
114                 kasan_check_write(to, n);
115                 res = raw_copy_from_user(to, from, n);
116         }
117         if (unlikely(res))
118                 memset(to + (n - res), 0, res);
119         return res;
120 }
121 #else
122 extern unsigned long
123 _copy_from_user(void *, const void __user *, unsigned long);
124 #endif
125 
126 #ifdef INLINE_COPY_TO_USER
127 static inline unsigned long
128 _copy_to_user(void __user *to, const void *from, unsigned long n)
129 {
130         might_fault();
131         if (access_ok(VERIFY_WRITE, to, n)) {
132                 kasan_check_read(from, n);
133                 n = raw_copy_to_user(to, from, n);
134         }
135         return n;
136 }
137 #else
138 extern unsigned long
139 _copy_to_user(void __user *, const void *, unsigned long);
140 #endif
141 
142 static __always_inline unsigned long __must_check
143 copy_from_user(void *to, const void __user *from, unsigned long n)
144 {
145         if (likely(check_copy_size(to, n, false)))
146                 n = _copy_from_user(to, from, n);
147         return n;
148 }
149 
150 static __always_inline unsigned long __must_check
151 copy_to_user(void __user *to, const void *from, unsigned long n)
152 {
153         if (likely(check_copy_size(from, n, true)))
154                 n = _copy_to_user(to, from, n);
155         return n;
156 }
157 #ifdef CONFIG_COMPAT
158 static __always_inline unsigned long __must_check
159 copy_in_user(void __user *to, const void __user *from, unsigned long n)
160 {
161         might_fault();
162         if (access_ok(VERIFY_WRITE, to, n) && access_ok(VERIFY_READ, from, n))
163                 n = raw_copy_in_user(to, from, n);
164         return n;
165 }
166 #endif
167 
168 static __always_inline void pagefault_disabled_inc(void)
169 {
170         current->pagefault_disabled++;
171 }
172 
173 static __always_inline void pagefault_disabled_dec(void)
174 {
175         current->pagefault_disabled--;
176 }
177 
178 /*
179  * These routines enable/disable the pagefault handler. If disabled, it will
180  * not take any locks and go straight to the fixup table.
181  *
182  * User access methods will not sleep when called from a pagefault_disabled()
183  * environment.
184  */
185 static inline void pagefault_disable(void)
186 {
187         pagefault_disabled_inc();
188         /*
189          * make sure to have issued the store before a pagefault
190          * can hit.
191          */
192         barrier();
193 }
194 
195 static inline void pagefault_enable(void)
196 {
197         /*
198          * make sure to issue those last loads/stores before enabling
199          * the pagefault handler again.
200          */
201         barrier();
202         pagefault_disabled_dec();
203 }
204 
205 /*
206  * Is the pagefault handler disabled? If so, user access methods will not sleep.
207  */
208 #define pagefault_disabled() (current->pagefault_disabled != 0)
209 
210 /*
211  * The pagefault handler is in general disabled by pagefault_disable() or
212  * when in irq context (via in_atomic()).
213  *
214  * This function should only be used by the fault handlers. Other users should
215  * stick to pagefault_disabled().
216  * Please NEVER use preempt_disable() to disable the fault handler. With
217  * !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
218  * in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
219  */
220 #define faulthandler_disabled() (pagefault_disabled() || in_atomic())
221 
222 #ifndef ARCH_HAS_NOCACHE_UACCESS
223 
224 static inline unsigned long __copy_from_user_inatomic_nocache(void *to,
225                                 const void __user *from, unsigned long n)
226 {
227         return __copy_from_user_inatomic(to, from, n);
228 }
229 
230 #endif          /* ARCH_HAS_NOCACHE_UACCESS */
231 
232 /*
233  * probe_kernel_read(): safely attempt to read from a location
234  * @dst: pointer to the buffer that shall take the data
235  * @src: address to read from
236  * @size: size of the data chunk
237  *
238  * Safely read from address @src to the buffer at @dst.  If a kernel fault
239  * happens, handle that and return -EFAULT.
240  */
241 extern long probe_kernel_read(void *dst, const void *src, size_t size);
242 extern long __probe_kernel_read(void *dst, const void *src, size_t size);
243 
244 /*
245  * probe_kernel_write(): safely attempt to write to a location
246  * @dst: address to write to
247  * @src: pointer to the data that shall be written
248  * @size: size of the data chunk
249  *
250  * Safely write to address @dst from the buffer at @src.  If a kernel fault
251  * happens, handle that and return -EFAULT.
252  */
253 extern long notrace probe_kernel_write(void *dst, const void *src, size_t size);
254 extern long notrace __probe_kernel_write(void *dst, const void *src, size_t size);
255 
256 extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
257 
258 /**
259  * probe_kernel_address(): safely attempt to read from a location
260  * @addr: address to read from
261  * @retval: read into this variable
262  *
263  * Returns 0 on success, or -EFAULT.
264  */
265 #define probe_kernel_address(addr, retval)              \
266         probe_kernel_read(&retval, addr, sizeof(retval))
267 
268 #ifndef user_access_begin
269 #define user_access_begin() do { } while (0)
270 #define user_access_end() do { } while (0)
271 #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
272 #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
273 #endif
274 
275 #endif          /* __LINUX_UACCESS_H__ */
276 

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